This application relates to the controlled deployment of recovery devices such as parachutes and, more particularly, relates to methods and apparatus that enable recovery devices such as parachutes to be deployed, when desired, to facilitate the safe return to ground of descending bodies such as components of a hobby or high power rocket that typically have been caused to separate at or near flight apogee once the rocket has lifted aloft its components and the accompanying recovery device.
An objective that can be addressed and admirably served by the inventive features that are disclosed herein is to increase the probability of a complete and safe recovery of a rocket when flown to high altitudes and/or when flown in breezy conditions, so that higher flights can be made than previously would have been attempted for the same field size and weather conditions.
As was disclosed in the FPA, it is preferable that hobby and high power rockets be flown only if they are equipped with suitable recovery devices or systems that enable components of the rockets to return safely to the ground and be recovered. A technique commonly used to initiate the deployment of a model rocket recovery device is to cause releasably connected components of the tubular body of the rocket to separate at or near the time when the rocket reaches the apogee of its flight, whereupon a recovery device is ejected from a compartment of the rocket body and promptly deployed.
Two of the more common recovery devices that may be ejected and deployed when rocket components are caused to separate are streamers that unfurl, and parachutes that unfold so their canopies catch the wind. The deployment of each of these recovery devices can desirably enhance the likelihood of safe recovery because each improves the visibility of the descending components, and each slows the descent of the components to minimize and hopefully avert damage due to ground impact.
Prior to launch, the separable components of a rocket usually are tethered together and to the accompanying recovery device(s) by what is called a “recovery harness” or “shock cord.” Upon separation of the rocket components, and upon ejection and deployment of an accompanying recovery device, the rocket components may tumble during their descent to ground. If the tethered rocket components are accompanied during their descent by only a small unfurled streamer that serves mainly to enhance visibility (i.e., if no other deployed recovery device such as a parachute is attached to the descending components), the components tend to descend rather quickly, usually without being wind blown away from the air space above the launch site. However, to slow component descent and minimize the detrimental effects that can result from high momentum ground impact, at least a small deployed parachute usually is provided to accompany the tethered-together components as they descend.
A problem commonly encountered when even a relatively small parachute is deployed at a relatively high altitude (e.g., at or near flight apogee altitude), is that winds aloft are likely to engage the deployed chute's canopy and carry the chute-supported components a significant distance away from the launch site before the tethered components descend to ground level. This may result in the tethered, parachute supported components traveling for miles away from the launch site before they land, being lost from view long before they land, and/or landing where they cannot be found or retrieved.
To ensure that separable components of the body of a rocket properly separate at or near flight apogee, and/or to ensure that a recovery device properly ejects (so it can promptly deploy) from the rocket body component or components used to carry the recovery device aloft, it is common to fire a black powder ejection charge internally of the rocket's body at the conclusion of the burn of a rocket engine (i.e., at or near the time when the rocket reaches the apogee of its flight), or to release a charge of gas such as carbon dioxide from a pressurized cylinder carried within the rocket's body. Either of these actions can cause an interior region of the rocket's body to become sufficiently pressurized to effect separation of adjacent tubular body components of the rocket, and/or to cause ejection of a recovery device which then promptly deploys, as by unfurling or unfolding.
If only one recovery device is ejected for prompt deployment by the recovery system of a rocket, the recovery system may be said to be of the “single deployment” type. If two distinct recovery device ejections are employed, each causing the deployment of a separate, promptly deploying recovery device, the recovery system may be said to be of the “dual deployment” type.
Single deployment recovery systems can offer the very significant advantages of simplicity, low cost and ease of use 1) because the same firing of an ejection charge used to separate rocket body components also can be used to eject a recovery device, 2) because the ejection charge to be fired can be built into the engine module used to launch the rocket to a desired altitude, and 3) because the firing of the ejection charge can be initiated substantially automatically by the engine module at the conclusion of the engine burn that lifts the rocket aloft. These features are well known to those skilled in the art, and engines of a wide variety of sizes and power that offer these features can be purchased from entities that supply the needs of rocket enthusiasts.
In a single deployment recovery system of the type just described, the ejected recovery device usually consists of a streamer, a parachute or a combination of a streamer and a parachute. Upon ejection, the streamer unfurls and/or the parachute unfolds to open as its canopy is caught by the wind—and all this takes place without having to provide, carry aloft or operate other apparatus such as a second or supplemental ejection charge, a cylinder of pressurized gas, an altitude sensor, or controls that may include electronic circuitry and a battery to power the circuitry—items that can add unwanted weight and complexity. The user simply selects the correct certified engine to launch the rocket, to separate its components, and to eject the recovery device; and, when the rocket is flown, the recovery device ejects and deploys at or near flight apogee in conjunction with the separation of the rocket's components.
Although the simplicity and minimal cost of single deployment recovery systems has resulted in wide use of this type of recovery system, the resulting slow, wind-blown descent of tethered rocket components supported by a recovery device such as a parachute that was deployed at a high altitude causes many reusable rockets to go unrecovered. This puts a significant damper on the willingness of rocket enthusiasts to launch until after others have flown their rockets and established that the winds aloft are sufficiently minimal (to minimize concerns about descending, recovery-device-supported components being blown away from the launch site and perhaps never recovered) to yield a reasonable likelihood of recovery. Moreover, the high probability of rocket loss associated with the use of single deployment recovery systems often causes rocket enthusiasts to severely limit the sizes of the engines they use, and the altitudes to which they launch their rockets, which can significantly diminish the thrill and enjoyment that are associated with the energetic liftoff and lengthy, sustained flight times of rockets propelled by larger engines that produce higher thrust.
Launch fields of small size, and launch fields that are bordered by restricted properties, by obstacles such as swamps, marshes, crops, powerlines, trees and the like, or by waterways such as streams, rivers and lakes, also tend to deter the flying of high power rockets because the slow, parachute supported descent of separated rocket components can subject the components to the influence of winds aloft, causing the components to be carried well beyond the bounds of the launch field to locations where the components either cannot be found or cannot be recovered. The recovery of a rocket is rendered safer if landed components need not be recovered from difficult terrain, and if rocket components are not found hanging on power lines, power poles, trees and the like.
When a dual deployment recovery system is used, it is common 1) for a streamer and/or a small parachute to be ejected and deployed at or near flight apogee, usually in conjunction with separation of components of the rocket's body, and 2) for a considerably larger parachute (a so-called “primary recovery device”) to be ejected and deployed once the tethered, separated rocket components have descended to a significantly lower altitude, preferably to a height that is only a few hundred feet above ground level. Although the task of providing a rocket with a dual deployment recovery system which includes a primary recovery device (typically a sizable parachute that ejects and deploys at a relatively low altitude) usually increases rocket complexity, cost, size and weight, dual deployment recovery systems nevertheless remain desirable inasmuch as their use can significantly improve the chances of locating and retrieving components of a flown rocket because the deployment of the primary means of recovery during only the final few seconds of rocket component descent minimizes the amount of time during which the descending components are supported by a sizable parachute that is likely to be wind-blown away from the launch site, hence the prospect of a sure and easy recovery is maximized.
What may not have been fully appreciated about dual deployment recovery systems is: 1) that regardless of the type of recovery device that is deployed by the system at a relatively high altitude, the deployed recovery device probably will do very little to address the very major concern that recovery-device-supported components will be blown away from the launch site and perhaps even lost to recovery; 2) that the deployment of almost any sort of recovery device at a high altitude may, in fact, exacerbate the problem of wind-blown component travel because the deployed recovery device adds significantly to the surface area (of the descending, tethered components) that can be engaged by winds aloft, and therefore may cause rocket components to travel farther from the launch site than they would have traveled if no recovery device at all had been deployed at a high altitude; and 3) that the one aspect of dual deployment recovery systems that actually does tend to help alleviate the problem (of rocket components being held aloft by a deployed recovery device that is engaged by the wind thereby causing valuable rocket components to be spirited away from the launch site) is the introduction into the recovery cycle of a delay in the deployment of a sizable recovery device until the separated components have descended to near ground level so the time of exposure to wind (of the sizable surface area of the recovery device deployed at the last possible moment) is minimized.
Stated in another way, in dual deployment recovery systems, it is the delay in the deployment of a primary recovery device (its deployment is delayed until near the very end of the descent of the tethered components when the tethered components are most rapidly approaching the ground, and when very little distance remains to be traversed until the components land) that causes the time to be minimized during which a deployed recovery device, such as a sizable parachute with open canopy, is exposed to wind that may cause the recovery device and the rocket components tethered thereto to travel a significant distance from the launch site. Moreover, because the wind encountered at ground level often is far less brisk than is the unobstructed flow of wind aloft, delaying the deployment of a sizable primary recovery device until descending components have nearly reached the ground often results in the descending components and their associated recovery device being subjected to winds of a less forceful nature than are likely to be encountered at higher altitudes.
If the delayed chute deployment advantages just described (that are associated with the use of dual deployment recovery systems) could somehow be combined with the earlier-described advantages of simplicity, low cost, low weight and small space requirements (that are associated with the use of single deployment recovery systems), perhaps the result of such a combination might provide recovery methods and apparatus that do not occupy much space, do not add much weight, are simple and inexpensive to use, and might therefor be suitable for use with rockets of a wide range of sizes including rockets of small size, to minimize the kinds of recovery problems described above that are commonly encountered with present day recovery systems.
Disclosed in the FPA are features of a parachute deployment control system that addresses many of the foregoing and other concerns and drawbacks of the prior art by providing methods and apparatus that can be used with descending bodies such as rockets that have been flown to desired altitudes to deploy recovery devices 1) at desired times, 2) at desired lengths of time after either a particular condition is sensed or a particular signal is received, or 3) promptly in response to a received signal for such purposes as minimizing the wind-blown airborne travel of the descending bodies such as rockets to facilitate recovery, preferably in reasonably close proximity to their launch sites.
Included in the disclosure of the FPA are methods and apparatus that can be used to delay the deployment of an ejected recovery device such as a parachute which preferably is retained in a compact, non-deployed form until the optimal moment is at hand for its deployment. The disclosed features can be incorporated into new rockets as they are designed and built, or may be added as retrofits to existing rockets. And, because the apparatus needed to implement these features can be quite small and lightweight, the disclosed features can be added to rockets of a wide range of sizes, including rockets of quite small size launched by relatively low thrust.
Although others have recognized the desirability of diminishing the time during which descending bodies (typically comprised of components that are to be recovered) are supported by deployed recovery devices to minimize the likelihood that the descending bodies and their appended recovery devices will be blown by the wind to undesirable locations where recovery may be difficult or impossible, the disclosure of the FPA recognizes and uses to good advantage the realization that a recovery device can be harmlessly ejected at a relatively high altitude to descend in a compact form with whatever needs to be recovered, if the actual deployment of the recovery device is delayed until its descent has reached a low altitude, whereupon the recovery device is deployed from the compact form in which it has been retained during descent, and the recovery device then serves to slow the remainder of the descent to ground. In this manner, the “descent slowing” function of the recovery device can be initiated at substantially the last possible moment before touchdown, the exposure to wind of the sizable surface area of the recovery device is limited to a final few moments of descent time, and the wind to which the deployed recovery device is exposed is mainly ground-level wind, often of less forceful magnitude than winds aloft.
As is explained in the FPA, the realization that a recovery device can be ejected harmlessly at a high altitude if it is retained in a compact form and not deployed until descent has progressed to a low altitude can be applied in a very practical way to the recovery of descending rocket components. One approach disclosed in the FPA is to modify a single deployment recovery system so that, when its ejection charge fires at the conclusion of engine burn, what is ejected at high altitude is not an immediately deployed recovery device such as a parachute that opens promptly in the wind, but rather a recovery device such as a bundled parachute that is retained in a compact, non-deployed form until the recovery device and rocket components tethered thereto descend to a low altitude, only a short distance above ground, where the recovery device is permitted to open. By this technique, deployment of the recovery device that was harmlessly ejected by an engine-carried black powder charge at the conclusion of engine burn is delayed until the optimal moment for deployment to take place, namely when only a short descent distance remains to be traversed. Thus, the “descent slowing” action which is initiated when the recovery device deploys, comes into play just when it is needed, and at a time when the deployed recovery device will be subjected to mainly ground level wind that probably will cause only minimal unwanted travel of recoverable rocket components away from the launch site.
Stated in another way, what is provided by one system disclosed in the FPA are the advantages associated with the delayed deployment of a recovery device in dual deployment recovery systems, and yet these advantages are achieved without requiring that the rocket being launched have sufficient thrust and load-carrying capacity to carry aloft the complex apparatus that are commonly associated with the firing of an auxiliary ejection charge in dual deployment recovery systems. Accordingly, delayed recovery device deployment is achieved in a far simpler way than it previously has been achieved.
Delayed deployment recovery systems that take at least one of the forms disclosed in the FPA can add so little weight to a rocket, and can occupy so little space that they are well suited for use with small rockets, even with very small rockets, to help ensure the safe recovery of their components. Moreover, advantages also obtain when a recovery device is retained in a compact form until the time for actual deployment time is at hand, for the compact form of such a device renders it easy to insert into the tubular body of a rocket, and helps to assure that, when the compact recovery device is to be ejected, it does not unfold, unfurl or otherwise behave in a manner that resists or impairs proper ejection.
Disclosed in the provisional applications (i.e., the referenced FPA and SPA) are a variety of forms of band like retainers—elongate band-like devices for encircling and retaining in compact form recovery devices such as streamers and parachutes. These retainers (whether taking the form of thread-like fibers that can be tied in place, or plastic band-like devices that can have one end region inserted through an opening defined near an opposite end region before being drawn up snugly) preferably share the characteristic of being heat-severable—a characteristic that permits retainers to be quickly, simply and easily severed by a localized application of heat energy to release for deployment a recovery device that is held in compact form until the retainer is severed.
Also disclosed in the FPA and SPA are control circuitry and devices for supplying electricity (at a desired time, in response to a received signal or at the expiration of a timed interval) to heating elements that provide localized heating needed to sever the retainers to release recovery devices such as streamers and parachutes for deployment. Introduced by the SPA are heating element modules (i.e., heating elements in a modular form) that plug into jack-like connectors of a control device or that can be coupled by modular connection cables to a control device in a way that facilitates the set-up of a rocket recovery device prior to the launch of a rocket, and that permits one heating element module to be quickly and easily substituted for another when this is desired.
These and other features, and a fuller understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawings.